Method for applying latex to deposition bases



Feb. 14, 1939. E, HANSEN 2,147,293

METHOD FOR APPLYING LATEX TO DEPOSITION BASES Filed Jan. 6, 1936 2 Sheets-Sheet l Feb. 14, 1939. M. E. HANSEN METHOD FOR APPLYING LATEX TO DEPOSITION BASES 2 SheetsSheet 2 Filed Jan. 6, 1936 Patented Feb. 14, 1939, 2,147,293

UNITED STATES PATENT OFFICE METHOD FOR. APPLYING m'r'nx 'ro DEPOSITION nAslls Merrill E. Hansen, Akron, Ohio, asaignor to American Anode, Inc., Akron, Ohio, a corporation of Delaware Application January 6, 1936, Serial No. 57,694

- l 10 Claims. (Cl. 18-57) This invention relates to procedure andgappa- Fig. 3 is a vertical section taken on the line ratus for applying coatings of latex to deposition 3-3 of Fig. 2; bases, especially deposition bases in continuous. Fig.4 is an enlarged vertical section showing strip or sheet form, and may be employed either a deposition base used for making rubber thread 5 for providing permanent coatings'oil latex rubaccording to the presentinvention with a deher upon such bases or for making strips or sheets posited rubber thread thereon of rubber by removing the deposited rubber from Fig. 5 is a vertical sectionlsimilar to Fig. 3 the deposition bases. Thus, the invention may illustrating a modification of the invention in be used for permanently coating paper, textile which flbrous material to be impregnated and/or ,10 fabric or the like on one or both sides with latex coated with latex is floated upon the surface rubber, or for making threads, strips, or sheets of the latextogether with a superposed sheet of latex rubber of any desired gauge and width. deposition base. In either adaptation the invention possesses dis- For the purpose of illustrating the coating of tinct operating and economic advantages, in adfabric or other material with latex using the dition to producing superior products. present novel method, I have chosen to describe 15 In its broad aspects, the present invention applying two coatings of latex rubber to the comprises utilizing a deposition base of suitable same face offi'a sheet 01' fabric, leaving the other form which is fioatableupon the surface of the face entirely uncoated and without any latex, latex or other liquid material to be' applied to although it is .to be understood .that through v the deposition base, and in floating the base upon utilization of the principles to be described, 0 e

the surface of the latex or other material to reor more than one coating of latex rubber may. 20 ceive the desired coating. Through this novele appl d t he h i s of t fa ri procedure one side only of, for example, a sheet by u ta e repe i i n of the coating p r of textile fabric may be uniformly coated with In a specific em odiment of th invention,

any desired thickness of latex rubber without aplust a ed in Fi a l o t xt fab c Ill 25 plying any substantial amount of latex to' the to be coated is mounted p n a suitable support other side of the fabric. Heretofore, this could for unwin a d t e a c is dir ed ove a be accomplished only by using relatively compllnumb r of positively driv n rollers designated in .cated and expensive spreaders or the like, and S e si n. I. ll, l n and h n o a can never be accomplished if the fabriejs 1 rewinding station I 6. The several rollers prefer 30 mersed in the latex as in the procedures for ably have fabric-gripping surfaces and are so 7 treating fabric with latex now most commonly disposed and their directionoi' rotation is such used. Similarly,-strips or sheets of rubber may thatthe fabric in passing from the roll III to the be made by stripping the deposited rubber from. i is caused travel alqng the deposition base, without any of the incon- Path f m free l heme 3 vemence and waste. accompanying the use of so arranged, in this example, that the same face deposition drums. or hands immersed in latex 9 the fabric is exposed at the bottom of each where rubber must always be deposited on porthe two loops 7 Under the bottom of each of the two fabric tions of the drum or band in addltion to the deloops is p-rbvmed a container, designated respec 4-0 sired and without the expense and tively Ila and llb, each containing liquid rubstating dimcmties accompanying processes such ber latex "a and llb suitably compounded, the in whmh latex is pnntwPnm t level. of the liquid latex in each container being .sltion surfaces. somewhat higher than the nornial lowermost Other advant es will be p n from t lfllwportion of the loop so that a substantial portion following detailed description of the inventionfas of the looped fabric will be in contact with and ex mplified bypref rr d m im n s, n w ich floating upon the-surface of the latex. It will reference will bemade to'the accompanying immediately be appreciated that close adjustf drewlngs. 01 which; ment of the latex levels in the containers is not Fig. 1 is an elevation in diagrammatic form necessary as the looped fabric will automatically 50 illustrating the present invention applied to the adjust itself to any variations in the level of the coating of fabric; l t x,

Fig. 2 is a similar diagrammatic elevation illus- A drying chamber I9, heated as by circulating trating apparatus for making rubber in sheet 'hot air, isprovided about a reach of the fabric form; p in its travel between the two latex containers, 55

of the fabric past the second latex container.

For coating most materials the dryers may be disposed as shown in the drawings, but if the material being coated has a reticulate structure as for example very coarsely woven fabric, it may in some cases be desirable to placethe dryers about the reaches of the fabric just after it leaves the latex in order to dry the latex upon the fabric at least partially before the coated fabric passes over the driving rollers and thereby to eliminate the possibility of uncoagulated latex flowing through the reticulate structure onto the rollers. Following the second dryer 20, a vulcanizing chamber 2i, suitably heated, is provided about the fabric. The fabric of course may be caused to traverse the length of the dryers and/or vulcanizing chamber more than once to effect the requisite heating for drying and vulcanization.

Having arranged the fabric and'apparatus as described. the several driving rollers are rotated at a suitable speed which, for example, will cause the fabric to travel at a rate of about five lineal feet per minute although considerable variation in speed, say from two to ten feet per minute, is possible without materially affecting the mode of operation. The rollers cause the fabric to travel along the path indicated, bringing it first into progressive floating contact with the surface of v the latex in the first tank ila from which it picks up a thin coating of latex 22a and then is progressively withdrawn from the latex and passed through the dryer is operated for example at a temperature of ISO-180 F. The apparatus is arranged so that the once-coated fabric is inthe first dryer for a time sumcient to set the latex firmly, a period of about flve to ten minutes at the Utilizing a compounded latex containing .cludingpapermAllsuch temperature indicated usually being satisfactory. The fabric with its somewhat dried coating of latex, continuing the travel along the path indicated, is brought into progressi oating contact with the surface of the latex in he second container ill) from which it picks up a second coating of latex over the first forming a composite coating of latex rubber 22 upon the fabric. The coated fabric then is thoroughly dried in the second dryer 20, forexample about thirty minutes at F. and the rubber coating is vulcanized as the fabric passes through the vulcanizer 2i operated at a suitable temperature dependent upon the characteristics of the particular latex composition in use. The finished fabric then is rewound or otherwise disposed of at the station l0.

total solids and having a viscosity of about "two andone hali' times that of water, theover-all thickness of-a sheet-of closely'woven cotton fabric was increased by approximately 0.005" by apply known and will be understood without detailed explanation here.

The present invention has been successfully used for coating and impregnating a wide variety of fibrous sheet materials including cotton, wool, silk, artificial silk, and the like, both closely woven as in fine silk fabrics or loosely woven as in cheese-cloth, as well as felted fibrous sheets ining two coatings of latex in the manner described.

If substantial impregnation of the fabric is fibrous sheft materials float upon the latex and may be efficiently coated or impregnated with latex in the manner described. Non-fibrous materials may be coated in a similar manner, and the invention has been successfully used for coating thin sheets of light metals such as aluminum foil.

In applying the present invention to the manufacture of rubber threads, strips, or sheets, all of which will hereinafter be referred to simply as rubber strips, or as rubber in strip form, I preferably employ a floatable deposition base to which the deposited latex rubber will not adhere so tenaciously as to render stripping of the rubber from the base unduly difllcult. For this purpose, I have used bands of paper, fabric preferably suitably treated to prevent tenacious adhesion of the rubber such as fabric coated with rubber,

rubber bands alone, and even thin flexible sheets of light metals such as aluminum foil, all of which float upon the latex. It is desirable however to provide for continuous operation by providing an endless deposition base, and for this purpose I have found a fabric band or belt, preferably coated with vulcanized rubber, to be quite satisfactory.

Such a floatable deposition base 30, (Figs. 2 and 3) for example, may consist of an endless belt of closely woven cotton fabric 3| thinly coated on both faces with vulcanized rubber 32, 12. The rubber surface of the belt may be suitably treated, as with a halogen, to render it less likely to adhere to the deposited latex rubber, but for reasons hereinafter to be indicated, such treatment will not be necessary in my preferred process.

, The endless deposition base or belt 30 is caused to travel about a series of positively driven rollers having frictional belt-gripping surfaces designated in succession 33, 34, SI, 30, 31 and 38 and past idler guide rolls 39, I! and a belt adjuster ll,

' the several rolls being so arranged and their direchorizontal reach and the first loop.

A tank 4| containing a liquid coagulant for rubber latex is placed at the bottom of the first free loop of the deposition base and a second tank 43 containing suitably compounded liquid rubber latex 44 is placed under the second loop of the with the liquidlevels injboth tanks some-'1 what higher than the normal lowermost portions of the loops so that a substantial portion of each of the two loops is in floating contact with the. respective liquids. s Adjacent the end of the long nearly horizontal reach of the deposition base is provided a washer consisting of a tank 45 containing water It and, above the water, a spray pipe 41 adapted to direct a'series of sprays of wash water downward upon material floating on the surface of wash water in the I A drying chamber ll heated as by circulatins hot air andincluding a suitable conveyor 40 passing through the dryer is provided adjacent the end of the washer, and a suitably heated vulcanizing chamber ll including a conveyor ll passing through the chamberis provided adjacent/the" dryer. Finally a wind-up station 52 or other desirable strip collecting apparatus is provided near the exit end of the vulcanizing chamber.

As may readily be appreciated from the drawings (Fig. 2) the endless deposition base in its continuous travel in the direction and along the path indicated will first be brought into progressive floating contact with the liquid coagulant 42 and that one face of the base will pick up a film or coating of the liquid coagulant, usually a solution of a polyvalent metal salt in a volatile solvent, and that the film or coating will dry somewhat as the base travels from the coagulant. Next the coagulant coated face is brought into progressive floating contact with latex M and a coating of latex coagulum 53 will be deposited upon the base as it floats across the surface of the latex. The

belt then will leave the latex carrying with it the coagulum which is permitted to become firmly coagulated and to dry somewhat as the base travels along the relatively long nearly horizontal reach. The .coa'gulum 53 is removed from the deposition base without difiiculty because of the separating qualities of the coagulant, and is thoroughly washed as by floating the coagulum upon upon the exposed face to remove residual coagulant and other water-soluble materials, after which the coagulum is transported through the dryer and vulcanizer. Finally the finished rubber strip is collected as by winding upon an arbor, or otherwise disposed of.

In making rubber strips in the manner described, details of operation will be varied as required in individual cases and as will be understood by the skilled artisan. For purposes of illustration, however, a typical'set of materials and conditions which have been used for making rubber sheet 0.012 to 0.0l5inch thick will be described.

Ina typical example, the endless deposition base is caused to travel at a constant rate of about seven feet per minute. The coagulant tank 4| may be about two feet long, and the latex tank 43 may be about nine feet long so that the base will be in contact with the coagulant for approximately one fourth of a minute and in contact with the latex for approximately one minute. The apparatus should be so arranged that about one minute elapses while the basetravels from the coagulant to the latex and so that about two minutes elapse-while the base travels from the latex to the point at which the coagulum is removed'from the base. The dryer 48 may be operated at 160 to 180 F. and the vulcanizer 50 at 220 F.

The liquid coagulant 42 may be a solution of 150 grams of calcium chloride dissolved in 1000 cc.

of methanol containing 20 grams of lactic acid as a wetting agent. The latex 44 may be an aqueous dispersion having a total solids content of 50% and containing 100 parts by weight of rubber added as the concentrated latex of commerce, 1.5 parts of sulfur, 1.0 part of zinc oxide, 0.45 part of an organic accelerator, and 0.1 part of an age-resister. I

In a further modification of the present invention illustrated in Fig. 4, rubber strips of U shaped cross section suitable for use as rubber thread have been made by progressively floating upon latex in the manner described a filamentary deposition base ofcircular cross section consisting'of a small fibrous cord 60 coated with. vul canized rubber 6| to provide a smooth deposition surface. In this procedure, latex deposits upon treated withcoagulant.

approximately half the circumference of the cord producing a U shaped strip of coagulum 62 whichcase it may sometimes be desirable to treat the latex upon the deposition base with c'oagulantin liquid or vapor form after the base leaves the main body of latex. For making thicker strips, the concentration of the coagulant and the time of contact with the latex may be increased, or the strip of coagulum may be removed from the deposition base and the .coagulum strip itself progressively floated across a second body of latex to build up'a thicker strip. If a coagulant or coagulant composition having a low specific gravity is used, the deposition base may be immersed in the coagulant rather than floated upon its surface as described. Similarly, fabric to be coated may be pre-treated with coagulant in which case the rubber deposit will be more superwash water and at the same time spraying water ficial than otherwise would be the case, or the latex after its application to the fabric may be It is also possible to float fabric, either wefted or weftless, together with a superposed sheet deposition base upon the latex in which case the fabric will be entirely submerged and therefore will be completely em bedded in the deposited rubber. Such procedure is especially useful for making rubber impregnated and coated fabrics for pneumatic tire manufacture. For example, referring, to Fig. 5, the apparatus of Fig. 2 may be utilized for 1mpregnating and'coating tire cord fabric by progressively passing a sheet of tire cord fabric 65 in floating contact across the surface of the latex ll together with the superposed sheet deposition base 30. As the fabric 65 is underneath the somewhat heavier deposition base 30, .the fabric will be substantially submerged in the latex and will receive a satisfactory impregnating and coating deposit of latex which is dried but not vulcanized, of course, if it is, to be used in tire manufacture. If a rubber coated sheet is desired for other purposes, the coatingobviously may be vulcanized as' well as dried merely by passing the treated fabric through suitable heaters as in Fig. 1.

It is of course also understoodthat any of the well known coagulants for latex such'as those disclosed in Willson U. S. Patent No. 1,996,090 may be used in the present process and that the term latex or liquid rubber latex" as herein used 1s intended to include all naturally occurring or artificially prepared analogous aqueous dispersions or emulsions of natural or synthetic rubber, the term rubberincluding caoutchouc,gutta percha, balata, and like gums, resins and synthetic products, whether such dispersions be concentrated, diluted, thickened, thinned, stabilized, bompounded, or otherwise prepared or conditioned for use. ..As has been indicated, the term strip or strip form is intended to include not only relatively narrow flat strips in the ordinary sense of the word but also filaments, bands, sheets and the like.

within the'scope of the present invention as de fined by the appended claims.

I claim:

70' All such modifications and variations are body of liquid rubber latex, providing a deposition base in strip form floatable upon the surface of the latex, bringing the deposition base progressively int'o floating contact with the surface of the latex, progressively removing the deposition base together with solids from the latex, and drying the latex solids.

2. The method which comprises providing a" body of liquid rubber latex, providing a deposition base in strip form floatable upon the surface of the latex, causing the deposition base to travel in a looped path with the bottom of the loop in progressive floating contact with the latex, and drying latex solids upon the strip after its contact with the latex. v

3. The method which comprises providing a body of liquid rubber latex, providing a body of liquid coagulant for the latex, providing a deposition base in strip form floatable upon the surface of at least one of the aforesaid two liquids, bringing the deposition base into contact successively with the coagulant and with the latex, at least.

one of the successive contacts being a progressive floating contact of the base with the liquid, and

drying the resulting rubber coagulum.

4.'In a method for depositing rubber directly from liquid rubber latex onto a deposition base, the process which comprises the step of floating the deposition base upon the surface of the latex. 5. In a method for depositing rubber directly from liquid rubber latex onto a deposition base by successively applying latex and fluid coagulant to receive a deposit of latex solids, and removing the deposited solids from the deposition base in strip form.

'7. The method of producing rubber in strip form which comprises providing a body of liquid rubber latex, providing a body of liquid coagulant for the latex, providing a deposition base in strip form floatable upon the surface of at least one of the two aforesaid liquids, bringing the deposition base into contact successively with the coagulant and with the latex, at least one of the successive contacts being a progressive floating contact of the base with the liquid, and removing the resulting coagulated rubber from the deposition base in strip form.

8. The method of applying rubber to material which comprises floating the material upon the surface of a body of liquid rubber latex, removing the material together with'associated solids from the latex, and drying the latex solids upon the material. g

- 9." The method of applying rubber to relatively long lengths of sheet material which comprises bringing the sheet material progressively into floating contact with the surface of liquid rubber latex, progressively removing the sheet material together with associated solids from the latex, and

drying the latex solids upon the material.

10. The method of applying rubber to relatively long lengths of flbrous material which comprises bringing the fibrous material together with a superposed impervious sheet deposition base into progressive floating contact with the surface of liquid rubber latex, progressively removing the flbrous material and superposed deposition base together'with associated solids from the latex,

separating the fibrous material and associated latex solids from the deposition base, and drying the latex solids on the fibrous material.

' MERRIIL E. HANSEN. 

